Two-hundred and forty-two tympanograms of infants were interpreted according to a standard operating procedure independently by an audiologist and ten study doctors from the Finnish Otitis Media Vaccine Trial. The interrater agreement among the study doctors according to Kappa index was excellent (kappa = 0.80). The agreement was significantly better on curves taken during pre-scheduled healthy visits than during sick visits due to respiratory infection (p < 0.001). In addition concurrent knowledge of the clinical ear status significantly improved the agreement on abnormal curves (flat B-curves and failed F-curves, p < 0.001). The clinical differences between the groups were minor. The age of the infant had no effect on interpretation. The agreement between the audiologist and the study doctors was also excellent (kappa = 0.77). Excellent agreement can be achieved in infant tympanometry through adequate instruction and training.